Telephone system



ug., 24, 1943. H. H. ABBOTT 2,327,481

TELEPHONE SYSTEM Filed July 22., 1942V 9 sheetsFsheet 1 Ang. 24, 1943. H. H. ABBOTT 2,327,481

TELEPHONE SYSTEM Filed July 22, 1942 9 Sheets-Sheet 2 MACH/N5' RING/IVG [IHI- ATTORNEY Aug. 24, 1943.. H. H. ABBOTT TELEPHONE SYSTEM Filed July 22, 1942 9 Sheets-Sheet 5 j; JPN

/NVEN'OR l H. H. ABBOTT ATTORNEV Aug0 24, 1943. H. H. ABBQTT 2,327,481

TELEPHONE SYSTEM Filed July 22, 1942 9 Sheets-Sheet 4 /NVENI'OR H. H AB80 T 7' ATTORNEY Aug.. 24, 1943., H. H. ABBOTT TELEPHONE SYSTEM FiledA July 22, 1942 9 Sheets-Sheet 5 /M/ENTOR H H. ABBO T 7' AT TORNE V I Aug 24, 1943 1H. H. ABBOTT TELEPHONE .SYSTEM Filed July 22, 1942 /A/VEA/rof? H. H. A3507' 7' f ATTORNEY ug. 24, 1943. H. H. ABBOTT TELEPHONE SYSTEM Filed July l22, 1942 9 Sheets-Sheet 7 /A/VENI'OR By H. H. ABBOTT AT TORNEV Aug. 24, 1943. H. H. ABBOTT TELEPHONE SYSTEM Filed July 22, 1942 9 Sheets-Sheefl 8 W k w1 VVE/WOR BV H. H. AB80 T T A7' TOR/VE V Aug. 24, 1943.

. H. H. ABBOTT TELEPHONE SYSTEM Filed July 22 1942 9 Sheets-Sheet 9 mum m m UrllD D D Uilm D D rlo )Ilo Patented Aug. 24, 1943 Telephone Laboratories, Incorporated, New

York, N. YW a corporation ofNew'York Appli'caiiin` JulyZZ, 1942,- Seriafl N0. 451,862

(c1. 1re-27)' scnims.

invention relates to-telephone systemsland particularly to private branch exchange systems wherein the linesare` interconnected by au-tomatic switches.

In large capacityprivate" branch exchanges it is commonl practice tol have an accompanying manual board by means oi* whichl incoming cenitra'l office calls canbe properly extended to the wanted subscriber. It isI also' common practice to have certain lines serving' important offices answered by the operators. Furthermore, means are commonlyprovided1 so that any subscriber by dialinga special number may gain the services of an operator.

lllicre the capacity of a private branchfexchange' of this' nature becomesfl'arge the limit of the capacity'of the accompanying board is approached. This limit is Xe'd by the capabilities Of the operators and the size' ofthe line appearances' which she may reach. The' present invention provides a means for increasing the capacity of a' private branch exchangevery muchV beyond the ordinary capacity of the accompanying "inanual board; In accordance therewith the oper'- ator's only partially complete a connection manuvally. Instead of having a line multi-ple 'before the operators a connector multiplev .is provided so; that in completing a connection the operator plugs into a line designated by a portion of the digits of the Wanted linel and thenr dials the remaining digits. Y Y

It is generally conceded that a four-digit system is about the limit to the capacity of a manu.- ally operated switchboard. Hence, Where the oapacity of a private-:fv branch` exchange requires more thanfour digits, other means must be employe'd.; According to the present invention, .the manualbcaid is `p iovi `iedwith a plurality of out'- ltsto e'achhundred group of subscriberslines s6 .that ina five-digit system the i'lrst three digits are manually selected and thelast twoare dialed.

The' system, therefore, embraces connectors reached by switch trains andother connectors Known as attendants connectors and the latter diner from the former in many respects. Since the operators use certain standardcord circuits,

the attendants connectorsk must" be made to produce the signals therein that are usually given when the cord is used'for itsordinary purposes.

Thus, the battery feed and'ringingarrangements fr. the calledsubscriber are still in the cord circuit andrnust, therefore, be eliminated from the connector and the connector must be further rno'died to allovvY thepassag'e cf these currents freely from the cord circuit Yto the called sub'- scriber; The connector must signal the cord circuitI to: thev effect that the line-'terminals of the called line have been reached and thereafter signal the idle or busy condition of the line and later the fact that the calledY subscriber has answer'ed.l

Heretofore a so-called universal cord? circuit has been used having a marginal relay in the sleeve circuit thereof.Y By thisA means the cord circuit is'ab'leL to distinguish between different kinds ofv lines; For instance, on= central oilce lines where dialing arrangements in the cord are required, ahigh' resistance sleeveI in the outgoing line is used and through the non-operation of a. marginal relay such dialing arrangements are rendered eiiective.Y On other lines, such as subscrbers lines no dialing is. necessary but ringin'g. current is needed. In this case the sleeve of the tie line i'smade of low resistance and so through. the operation of the said marginal relay the cord circuit is so aiiected that the dialing circuit i's rendered ineiiective and' the ringing circuit'in'. its place is Vrendered effective. Such prior' art arrangements merelyrdistinguished between d'iiierent types ofo'utgoing lines and made suitable arrangements in the cord' circuit to cooperate therewith. In this connection reference ismade to Patent 1,866,260 granted' July 5, 1932,

`to King 'et al. and Patent 1,851,669' granted October 11, 1932, to King et al.

Other prior -art arrangements used other methods of discrimination between the types of outgoing lines but used what is termed sleeve supervision. By Way of example, Patent 1,675,956 granted July 3, 1928, to L. F. Porter shows the use of a marginal relay in the-sleeve of the cord circuit which responds to a supervisory signal in theV form'of a change in the resistance of the sleeve of the cooperatively associated circuit.

I'n accordance with the present arrangement, the marginal relay in the sleeve of the cord circuit'is used for both purposes, that'of discrimi- Hating between types of outgoing lines and that of" passing supervisory signals@ Thus, the attendants connector jackrcircuit is provided with a normallyV high resistance sleeve circuit whereby the dialing circuit of the cord is rendered effective. When the connector is thereby driven to the line terminals of the wanted line the sleeve resistance is lowered so that the marginal relay of the cord circuit operatesV and -now renders the ringing circuit of the cord eliective in place of the dialing circuit. Thus, the normal arrangements of the cord circuit are used advantageously to perform an additional function.

Reference is made to the copending applications Serial No. 451,863 led in the name of C. D. Koechling and Serial No. 451,918 iiled in the name of A. S. Martins on even date herewith, both of which applications cover inventions based mainly on the same disclosure as that herein set forth.

Other features Will appear hereinafter. l I

The drawings consist of nine sheets of circuit diagram.

Fig. 1 is a schematic circuit diagram showing the general plan of operation and indicating the arrangement of the remaining figures;

Figs. 2 and 3 placed with Fig. 3 to the right of Fig. 2 show a co-rd circuit and Fig. 4 placed below Fig. 3 shows the operators telephone and dial circuit all used at the manual switchboard used in connection with a dial private branch exchange;

Fig. 5 shows an outgoing trunk circuit cooperating with the cord circuit of Figs. 2 and 3 by means of which the operator may control the distant connectors of Figs. 6 and 7;

Fig. 6 shows a distant connector over which an operator may reach any one of a group of individual lines;

Fig. 'I shows a similar circuit arranged for trunk hunting over which an operator may reach a group of lines arranged in subgroups;

Fig. 8 shows an operators connector cooperating with the cord circuit of Figs. 2 and 3 over which an operator may reach any one of a group of individual lines; and

Fig. 9 shows a similar circuit arranged for trunk hunting over which an operator may reach a group of lines arranged in subgroups.

The system herein disclosed is a dial private branch exchange system so large that it is beyond the capacity vof the manual attendants board. It is common practice to supplement a dial private branch exchange system with a manual attendants board where incoming calls are answered and certain other special service is given. Generally speaking, a manual board has a capacity of about ten thousand lines or can handle only four digit numbers. But it is possible to employ a system of much greater capacity for private branch exchange service. 'Ihe present System is shown as a five-digit system, though it may be of even greater capacity.

Since the number of lines to be served, is beyond the capacity of a manually Voperated switchboard the operator is not given direct access to any of the lines but selects an outlet bearing the first three digits of the number of the wanted line and then dials the last two digits thereof. Y Thus, by way of example. if the operator wishes to establish a connection to line numbered 12345 she will insert her calling plug into a jack designated 123 and then dial 45. By thus setting up a connection partly by a manual op,-

eration and partly by an automatic or dialing operation the operator at such a switchboard may reach any one of a number of subscribers more numerous than could be reached by' conventional methods.

In Fig. 1 thereiare shown two ordinary private branchexchange lines terminating in stations I and 2, each equipped with a dial.V These station lines appear in a line finder 3 and by dial control may operate ar rst selector 4, a second selector 51, a third selector Ii and a connector 'I al1 in conventional manner. Thusthese stations may be interconnected by ordinary and well-known means. As indicated in this Schematic any one of such ordinary stations may dial 0 and reach an operator through an answering jack appearance 8. Such a Station by dialing the digit 9 may reach a central oice 9 over an outgoing trunk I0. In the same manner any one of these stations by dialing 8 may reach a distant private branch exchange II over a. tie line I2.

There may be provided certain special lines for high ranking oiiicials such as those terminating in stations I3 and I4 which do not appear in line finders, but, on the other hand, have special switchboard appearances l5 and I5, respectively, so that outgoing service is on a manual basis. These lines have appearances in the bank of the connectors so that they may be reached automatically.

Incoming central office lines and tie lines have manual appearances such as I'I and I8.

The operator may answer a call at any one of the appearances I5, I6, I'I or I8 by means of the answering plug I9 of the cord circuit 20 and by means of the calling plug 2| may establish connections to any one of the stations of the private branch exchange. It is understood, of course, that the operator may also extend connections to the central ofce 9 and the distant private branch exchange II, but these arrangements are well known and do not form any essential part of the present invention. It may also be noted that the distant private branch exchange l I may be the same as the distant private branch exchange indicated in the broken line rectangle in the lower right corner of this figure. In the one case the tie line I2 leading to the private branch exchange is answered by the operator thereat and in the other case a connection may be extended from jacks 22 or 23 directly to a subscriber in such distant private branch exchange.

Locally the calling jack 24 leads to a connector 25 by means of which the operator may extend a connection to any one of one hundred subscribers lines -in the group designated by the threedigit number distinguishing the jack 24. In the same manner the operator may employ the jack 25 to reach any one of one hundred lines characterized by the same first three digits which distinguishes the jack 25. However, this connector 21 is arranged forY trunk hunting and if driven to the proper level will automatically pick out the rst idle one of stations 28, 29 and 30 by way of example.

Cord circuit It will appear hereinafter that the cord cir-l cuit shown in Figs. 2 and 3 is arranged to cooperate with various lines provided with a connection to battery on the sleeves thereof. When vperforms no useful function at this time. Relay 34 operated closes a circuit from ground through itsv armature and front contact and the winding vof: relay 35 to battery whereupon relay 35 operates and at its armature 5 and back contact opens a circuit for relay 36. Through the operation of relay 35 a circuit is closed from the tip asomar ort-he plug; 3512, springsrZ and-3'of:therii1eiugkey 31, upper winding OLreIayrl', `springsglllof the;Y key: 395,. armatura. Il ,amm front; comet. of releryr. armature 3 Back: of: relay 420,1 upperswinding. of relayxltlzto ground.. Atzthe same a circlntzrnzaytbentraced;.fromtrrea ring ofiplug'zt throughA springsaiamil ofthe-.ringing 3.1.1,. lower Windingioffreiay.3a;. sprirrgs:. l le and lfifof key S'Barmaturera andbaekcnntactmf relay? d', the Iower..winxzling1 of: relay: tl toi hat; texy.. Relays 33K* aznd M2 both.. operate dues. to cixurernriloWirug:throughi thefcircuit: just: described androyer the bridge provided: bythef-calling'rline circuit. E01: a. understanding of? the nmtnreo such .calling line-circuit: reference. may be' lraid. to application. filed 1 Bascom'; and Lamberty, Serial No. 433,583); April: rr, 19.492.;

Relay S operated: prevents the rearcord supervisory lamp: 32: from. lighting while the relay' 41 operated..perforar-is nofusefulfimction at this timeV The: a'ttendant',v after reserving the requirediv infimnaiionz from: thel calling` station., makes-the usuailbusy test with the. tip: or the frontcord 142 and if thewantedffline: is: idle, insertsthe plug et tireY fronts cords' inthe jack'. offthe `called line operating.V relays 43 and? 44 in series.

Relay 4.3 operatedl establishes! a circuit from its.- armature andi front' Contact through Wir-loing. of.- relay 45 to battery, causing tie of relayv 415` Relay 44 iin operating establislresj a circuit from ground, its armature and' front Contact, through the'- Wrrrding of relay 4&.to1- battery whereupon relay 426- becomes operated. A circuit may now hev traced from ground, resistance 41B, armature and front contactfof'relay', armature lf and bac-k contact-of relay 49,. the lower winding of relay 47,' springs 8 and' S' of key 38, front contacthand armature 6 of relay 45 toA battery. vlt'elay operates and locks in a circuit from ground', springs Bland l ofdkey 3S, armature 5 an'd'frontfeontactof relay 3.5', armature? and front contact of relay li?, the upper Winding of relay 451, bac-k conta-ct and armature 3'. of' relay 5l), springs Sfand' of key 53', fronti Contact and armature 5" of' relay 45" to battery.

The operationof relay 44"- prevents theopere ation or relay 4u when relay 451 is operatedy by relay 43.. The' purpose ofthi's will appear-here'- inarter. Relay @operated/"causes theY front cord supervisory lampV 5l to'li'ght under control of relays- 4G, 52fandf 5.3i. A circuit may betraced from battery, lamp 5I front Contact and armature Sy of relay 45, armatureli and front Contact of relay S5, back' contact andarmature l of relay 54, back Contact and armature of relay resistance 55 to ground'. The operation of relay 45 also opens a retardation coilb-ridge circuit across the tip and ring of the rear cord iw-hich, up to this time has beenV open at the contactsof relay 45'. With relay 45 operated and relay ,46 unoperated' a -bridge circuit maybe treated from the tip of plug 3l, springs' 2 and 3" of key 31', upper Winding of'relay 33, springs 4l and' 5 of ley 35, hack contact and' armature 2 of relay 46', front Contact and armature 2 of relay 45', back contactand armaturetof relayr, retardation coil 58, armature l and back- Contact of relay itl, armature 3 andback` contacter, relay 35, springs I5 and l I4 of key 39, lower Winding of relay 33', springs 4 and 5f of keyv 31 to' the ring ef plug 3l. This circuit, though closed. byar'- mature 2 of relay 45, is opened by armature 2 ofrelay 45. Relay t5 operated removes' tlie'busy testel'ead 55 from the tipioffthe front cord,.,con.V nests the tipiand ring of the cordzthroughthe contacts.y of' relay 5T and-1 disconnects battery through resistance 58 from theririgv of vtheflcmt cord' plug-. Relay` 46r operated connects. the windingsl of: relay 52' tothefront contacts ofrelay 5l'. A circuit may. betraced from the tip of plug 42 through armature. 4 and front Contact of relayv 45,.armature-3 and frontA Contact of relay 46:; springs. 4: andi'of relayV 51'; armature 4 and frontfcontact ofrelay 325 to one side ofthe source ori ringingf current 59, The ring conductor vmay he traced-from the ring of plug 412 through armatures-51 and. front Contact of relay 45, armature v4 and front.y contact ofA relay 46, armature Eiland baclricontactof relay 5T through the upper windi'ng'oi-relay 5?, armature Siand front contact of relay 35 to the-other side of the source of ringing current. SEL' so that ringing current is now supplied'to'the tip/and'ring (sf-theplug 42 with the upper. Winding of tripping relay 5T in series therewith'. The source of ringing current' 5S represents the usual'machi'ne-ringing source and may be applied at intervals through an interruptor.' During ringing part of the ringing currentk flows through condenser '3Q-'in a circuit which may: be traced from armature 6' of relay 5l through armature Sandi frontV Contact of re lay 4J; armature E and front Contact of relay 4%., condenser 66, springs-5 and 4 of front cord ringingv Si, springs Il!` and I2 of key 39, springsl 8 and tof talking key 62, armature 8 and haelt` contacto-l relay 4t, lower winding of relay 52 toV battery and' in parallel therewith through condenser 53, back' contact and armature Tor relay 40, armature 6 and back Contact ot'relay 40 and thence through the lower winding ofvrelfay Mito battery. Tliroughrthe connection of ringing current to the lower Winding of relay M, a ringing tone is transmitted back to the ca gestation' as an indication thatfringing current sbeng connected to Vtrie calledstati'on line- When the receiver called station is removed from the switchho'ck thetrippin'g relay 51 operates. VThe relay 5T thereuponv substitutes the winding of relay 5.2 to the tip and ring of the called line irr-place-of the source of-ringing currentl 55 and 'locks through its lower winding, its: contact 2 and armature I to the front Contact and armature `I or Vrelayv 45.' Relay 52, noW in circuit: with the called station, operates andcauses the iront cord supervisory lamp to be extn guished and the relay 54 to operate through its lower Winding. The circuit for relay 54 may be traced from ground; resistance 55, armature and front contact-of relay`52., armature 3 and'back contact cffirelfay 53, lower Winding of relay 541, trol-1t` contact and'armature f of relay 46 to springs-'eatin 9f of key 35, front Contact and. arm ature 5 of relay- 45.- to battery. Relay 54 locks in a, circuit from ground', nermal contacts of arma.'- ,ture` 4 of relay 55", armature-2 and'fron't Contact of. rel-ay 54, upper winding of relay 54 through back Contact andarrnature 3V of relay Seto battery oyer,A the. circrL't hereinbefore described. Re'- layV 54 thaefore locks under control of` relays 55.,.45, and 46 and partly provides anoperating path forV relay 53- i Frornthe oregoingwe'can summarize as follows (A) Battery and ground for the-calling station are. furnished by the cord circuit through the windings of relays 4! and 38.. (B)v Battery and ground'for the calledstation are furnished the cord circuit through windings of relay 52'." (C) The front and rear cords are coupled through condensers 53 and 64. (D) No bridge is connected across the tip and ring of the cord, except the ringing relay 61 which has no useful purpose at this time.

When the receiver is replaced on the switchhock at the calling station, relays 4I and 33 release causing relay 49 to operate under control of relays i] and 33. The circuit for relay 45 may be traced from battery, armature 5 and front Contact of relay 45, springs 9 and .3 of key 39, armature 3 and back contact of relay 59, winding of relay 49 through the normal contacts of armature 2 of relay 49, armature 4 and front contact of relay 41, back contact and armature of relay 38, through resistance 48 to ground. Re-

lay 49 operated locks through its front contact and armature 2, front contact and armature 5 of relay 35, springs 1 and 6 of key 39 to ground. The rear cord supervisory lamp 32 is now energized in a circuit from battery, lamp 32, armature 2 and front contact of relay 35, armature 4 and front contact of relay 49, resistance 43 to ground. The lighting of lamp 32 operates as a disconnect signal.

When the receiver at the called station is replaced on the switchhook relay 52 releases causing relay 53 to operate under control of relays 50, 45 and 45. A'circuit for relay 53 may be traced from battery, armature 6 and front contact of relay 45, springs 9 and 8 of key 39, armature 3 and back contact of relay 5S, winding of relay 53 through the normal contacts of armature 2 of relay 53, front contact and armature I of relay 54, back contact and armature of relay 52 through resistance 55 to ground. Relay 53 locks through its front Contact and armature 2 to the normal contacts of armature 4 of relay 50 to ground. The operation or relay 53 now lights the front cord supervisory lamp in a circuit which may be traced from battery, lamp 5I, front contact and armature 9 of relay 45, armature 6 and front contact of relay 45, front contact and armature I of relay 53, resistance 55 to battery. This lighting of lamp 5I operates as a disconnect signal. The operation of relay 53 in opening the path of the lower winding of relay 54 at its back contact and armature 3 thereupon opens the original operating circuit of relay 54 but this relay remains operated through its upper winding. When the plugs of the iront and rear cords are withdrawn from the associated jacks all operated relays release and the circuit is restored to normal.

Flashing recall If before the plugs of the front and rear cords are withdrawn from the jacks thel switchhook at the calling station is operated and released to recall the attendant, the relays 4I and 38 will release and reoperate. The relay 38 in releasing causes the operation of relay'49 in the manner hereinbefore described. Upon the reoperation of relay 38 the rear cord supervisory lamp is now connected in a circuit which may be traced from battery, lamp 32, armature 2 and front contact of relay 35, armature 4 and front contact of relay 49, through the resistance 48 and in parallel therewith, the armature and front contact of relay 38, armature I and front contact of relay 49 to the flashing recall lead 65 which essentially supplies interrupted battery to periodically shunt the lamp 32. This causes the lamp to flash. The attendant then operates the talking and dialing key 62 causing relay 5i! to operate which releases relay 49. Relay 49 released, stops the flashing of the lamp 32.

If the switchhook at the called station is operated and released, relay 52 releases and reoperates. Upon .the release of relay 52 relay 53 is operated, as hereinbefore described. With relay 52 reoperated the front cord supervisory lamp 5I is connected in parallel with the ilashing recall circuit in a manner similar to that hereinbefore described so that lamp 5| now flashes. The attendant then operates the talk and dial key 52 causing relay 50 to operate. Relay 50 operatedreleases relays 53 and 54. Relay 53 released stops the flashing of the lamp, When the talk and dial key 62 is restored to normal, relay 55 releases and relay 54 reoperates, as described hereinbefore.

The above description applies to the use o! the cord circuit when a connection is being made between two local lines as, for instance, a connection between the stations I3 and I4. In the schematic shown in Fig. 1 it is not contemplated that the calling cord 2l will be used for directly calling a local substation though it is capable of this use in the manner above described.

It should be noted that both the answering and calling cords have two relays in their sleeve circuits, one of which is marginal. Thus, for instance, the sleeve of the answering cord has the two relays 33 and 34 in series, the relay 34 being marginal and only operating when a line sleeve of lower resistance is encountered. In the same manner the sleeve of the calling plug 42 has the relays 43 and 44 in series with it, the relay 44 being marginal.

It will be noted in the description to follow that the sleeve of the line leading to an attendants connector as, for instance, from the jack appearances 22 to 25, inclusive, has a high resistance when it is selected and maintains this high resistance until certain operations are completed, after which the resistance is lowered. Therefore on a call from a station to another station via an attendants connector the marginal relay of the calling cord will not be operated at first.

When completing a call from an attendants trunk, such as that terminating in the jack 8, or from a manual station, such as those terminating in the jacks I 5 and I6, to a station via an attendants connector, the operation when the call is answered with the rear cord is the same as described hereinbefore. However, when the front cord is inserted in the jack associated with an attendants connector relays 43, 45 and 40 operate since the sleeve resistance is high. Relay 45 operated disconnects the relay battery supply from the rear cord but the calling station receives battery from the connector in the manner which will be described hereinafter. When the operators dial is moved off normal for the first digit the rear cord is fed battery and ground from the telephone and dial circuit and the front and rear cords are separated in the dial circuit. The attendant then dials the two digitsrequired to bring the connector to the desired line.

The attendants connector will cut through on the called line if it is idle and the battery and ground from the tip and ring of the connector will be removed. At this time the connector also changes the resistance on the jack sleeve from high to low. The change to a low sleeve resistance causes relays 44 and 45 to operate which in. turn causes relay 40 to release. The release of relay 40 reconnects relay 4I to the rear cord and separates the' rear andfront cords by condensers Gfan'd PE4. :The Aconnector is hel'drof normalunL der ico'ntrol 'ofz'the "sleeve :after cut through :and the it1p.andring; 'o'f the. front cord .are connected to theback contacts of the tripping relayilito .transmit machine-'ringing current to tlfexcalle'd f subscriber. Audible ringingtone `is transmitted toward :the rear-cord through condenser 1.6'0 'as herenbefore described; Relay 54B `closes the windings ofrelayy 52rtorthe front contactsyo'f the tripping relay 51 to supply talking battery tofrthe called lin-'e after tripping relay .51. operates u-pon the response of the called party.

When the f called :station answers, relay $.51 operates .andfrlaysxl 53 an'df54 unctionas described hereinbefor. The'talkingg signalingy Y 'operaterand release `,relay 52-5s`t'arti'ngg Flash? nglrecallslnall on thefro'nt cord larnj; l1f the attendant-hais `not restored the tzlk and dial keyfez .win z receive: an audible busy4 marca: IL Y 'llt-ris' particularlyto be noted thaty the interrupt; er in theatteneantfs connector circuit which in: trmittently 'applies-tbe `bridge13o-the tip #and ring :of the calling .cord G2 is of one-halfftlfl'e rate of -thehihterrupter By Way of example, th interrupterlA Gli appliesV battery to the leadv--SSflt the rate'fof 12)` Iimpulses p'ervmlnutewhile the-in; term-plier? in Vthe attendants connector. crcut lur'rslat'4 thev rate of inte'rrup'tons perinin'lt. 'Since' the nterru-pter -inwthe atte'hclantsv connectoxcircuit.operates the relay-52 itwlill there; fore-render? the-nashingrecall circuit ot this cord ycircuit .Ieictve On every `-c'tl-er interruption thereof so tnatirnevelfect is that the lamp 5l Wijn he fli.; :approximatelythree-tenths of a period .and dark.therother sevenetenths thereof.' The signal 11'01".' the recalll is. af'- s'teady flash-lng at'. "the fate' of 12o. interruptions: per minute,- whileftlre signalnfonthe neormterzof. a busy condiments this soi-'called syncopated lsignal .wherein every other flash-of thesgnal invite; 4oridi'nairy-tvirlrlki'r'ig' is-rendered ecti/e. -Sirr'cnthefinterrupter of the-.attendantfs :connector circuit and the :interrunter' Satire-.both operated from the-samenwer .plant they may. both `:bef yonV the the: relationl .between them; :may bei Xed.

:Thezoperation ofthe cord circuit on a-conneci tion between'fa centralol-'c'e calrland asta'tib' is .a-s.. follows: the incoming central'. rof'ce callI vis answered. .with the rear :cord 35| V1in' the usualm'an .ner .and the operation is' [different from. .lzlnad'fr''ef-l scribed hereinbefore'sn th'atahighlsleeveresistanc'e `is encountered .which does l not' valloy@l 1 the marginali relay 541 to respond. Sncethermargi': nal r'elaydoes not respond; therefore relay 35 does not operate.L 4.Asia result a connectionV is. establishe'clfrm yground,.springsi-fE31: and' 1 .orkey 3'9, armaturenf and lback contact of. relay. 35;fronti Contact.` and armature Y:of relay!v 33; winding of relay 36' .tol tery.V As a resultofthe operation ciV relayii a'ffconnection may he traced from' groundfat the armature zand backzconta'c'tfof relay 34",` larmature landfrontchta'cttof: relay 36, Winding of; relay 451 tohattery` and: .groundwhereuponA relay ".149

same shaft-.alud

becomes operated. .lheblerationofathese relays connectsa fbrdge :across .the cord -.;wh0h may .beltraced from the tin 'of plugm sprinesgand .ofthe rng'nerkey Sl'efront contestarle armature 3f of. relay. gcretarjdaton :coil 68;, armature lgand back .contact :of relay-A1,: armature A.8, and front contact of. relay 35e-.springs I4 andeof ringing-key 4alto the ring ofcplug 3l; lThis hrldeeseryesas a signal on the central oce line thatslthe call has been answered andwillrservetotrp ringing. and .performl the. other usual functions required in .23 caseof this kind.. l

'When the ircntcord s-,i'nserterl inthej'ack of -an 1 .,attenoants. connector relay ,T38 operates and .Causes .the operation ,of `relay 41 on its lower winding. d n

. fA;cir'cuit may be traced .from..gr.lmd. on the tiplzof. vcordial .springfz and 3f o'f ringing;.key.:31, upper. WindingV oirrel-ay 138, springs; 4 andi ofkey l$9; front contact-and armature 'r1 ."o'f relayr'l, V'springs ,landefnf key -.62sprngsi|z and I3'.-,o'f key :35; springs 4 and 5.!o'f key IBI', hack contact and armature 4 of relay 46, front contact ahd armature `li of :relay..45; to the rin-g'. .of @1115.42 wnereitoencounters battery. in .the circuino'f the attendants connector; i'LikeWise; acrcuitmay lloe-.tr-.aced fromf-battery on the ring fof lcordl, Springs .5.andf4 of .keyi.3.1, lower v.Winclingfof relayV vMi; front .f Contact .and 1 armature 4 o..relay.45

to: theftip ofv plug 42 .Where it encounters Aground in the circuit of the attendants connector; 'fRe'- layfa responds and closesfa crcuitifromeround, .resistance.:48;.armature .and front. Contact .of relay; rmatlrefl and'loackxcoritact ofrlyl, lower-winding .of relay; 41; `springe 8 .and :9Y vof key 39; front contactand arma ure' i df-rlayS to cause thefopration .or relay 41: l

.Relay 38 ...will release' 'Wl'ren-` the dia1lsmod orf normal .b'u't vrelaylts will not operate andrely 4'1 .will releasesi-rrce the. talk-and dial ky 6221s operated: Movin-'g thesdalonnormal separates the front and rear cords. The atte'ndant` then dipalslvthehtyyo digits `to Vdirect the. connector to the t The attendants connector cuts through on the called line if it idl'; removing the battery @daer-0.1111@ .fleralhep and. .rma an@ @han the.; la?? .sleeveiresleta @e .assqciatqtw, t0 e. latter @lue T.hlf'esfrelevs A41. mi relay Mhremaesppereted veder.- QQIltfp-ltefs, ley. tiefen@ fingef .thefreet 1911@ eminem@ -nectelztoobm cpu- 11etS;,0-t1fippi,ee relay 5l f9.1@ the trensmllssmn .-.Qf

rl rig-,curr rrjgfhllhe.A callin-lampl willy also v. .c ..1 1 nel when the. @elimination Lauwers .theriphieg relay 51. operates and closesthroyghlthel@pand ring of the front cord. v'lheground' that locks relay 51 operated also-*passes over lead (i9 to the telephone.- circuit aindvzcauses a', relay therein to operate: andz-iurnshta-lking :baitteryto the .called station- .until the'vtalkingfkyg isfrestored: by the attendant. Whencthe talk ,and dial zkeyglisrestoredf tplhormal;theehattery Aandi ground from .the :central oice is A fed through-i the'. windings of relay .to ,the calledr. station.' @R'el'ay' .Will-op'- le'rate?ranch fextinguishethe' .calling Aline lamp' i5 ly .at this V,t'inenand? relay 41* W'll operate, opening the shortcircut about' resistancez `.vlhereby'#less current: fromtnexcentralioilce' .line` isf'dralned'by the-hufirfgezandt'za'4 greatera'mount allowed' .to drow to the called station. The operations in this connection may now be summarized as follows: (A) Talking battery for the called station is furnished from the central oiice. (B) A high resistance bridge consisting of the winding of retardation coil 68 in series with the resistance 10 is bridged across the tip and ring ofthe rear cord. (C) The supervisory relay 38 is under control of the called station.

When the receiver is replaced on the switchhook at the called station the circuit functions, as described hereinbefore, except that relay 38 is under control of the called station and the operation of relay 49 causes the front supervisory lamp to light as a disconnect signal and short circuits the resistance 19, thereby decreas- -ing the resistance of the bridge across the cord.

Flashing recall is controlled by relay 38 in conjunction with relays 41 and 49, as described hereinbefore. However, since relay 35 is not operated the supervisory lamp of the calling cord is ilashed rather than the answering cord lamp 32.

. If the called station is busy the sleeve becomes low in resistance and the battery andV ground are removed from the tip and ring in the connector and replaced by a bridge which is intermittently applied. If the talkand dial key 62 has been restored to normal the application of this bridge will cause the supervisory relay 38 to operate and release, thereby starting the flashing recall signal on the tfront cord lamp. If the attendant has not restored the talk and dial key on a busy connection she will receive an audible busy indication.

In the nrst, case, where the busy indication comes in from the attendants connector circuit the bridge will be applied to the tip and ring at the rate of 60 interruptions per minute and this will so eect the ashing of the lamp 5| at the rate of 120 interruptions per minute lthat every other flash will be eliminated, resulting inzWhat is spoken of as a syncopated signal in which the lamp 5| is lighted`--ior approximately threetenths of a period and dark for the remaining seventh-tenths.

TELEPHONE AND DIALNG CIRCUIT ARRANGED FOR Usn WITHv Ar'rENDAN'rs CONNECTORS When the tip of an associated cord, for instance, plug 42, is touched to the sleeve of a busy station line, tie trunk, attendants connector or trunk jack, ground or positive potential from the busy sleeve charges condenser 1| through a winding of the repeating coil 12 and resistance 13 to the front contact of relay 14, this relay being energized through the transmitter 15 of the telephone set. This induces a busy click through the winding of the repeating coil 12 at the at- -tendants telephone receiver.

Talking When the tank and dial key 62 of an-associated cord circuitis operated the leads 16 to 80, inclusive of the telephone and dial circuit are connected to the cord circuit, thereby closing the tip, ring and receiver leads and providing a talking circuit for the attendant. The attendants transmitter circuit may be traced from ground, the right-hand lwinding of repeating coil 8|, through the tip of jack 82, transmitter 15, the tip of jack 83, the winding of relay 14 to battery. Speech currents from the transmitter 15 are then transmitted by the left-hand windings of repeating coil 8|, through the back contacts and arma.- tures 2 and 4 of relay 84 to the talking conductors and 89. The operators telephone receiver circuit may be traced from conductor 85 through the back contact and armature of relay 81, back contact and armature'l of relay 84,.the sleeve of jack 82, the telephone receiver 88, the sleeve of jack 83, armature 3 and back contact of relay 84, the mid-point tap on the left-hand winding of repeating coil 8| through the condenser 89, back contact and armature 4 of relay 84 to conductor 86. Through the back contacts and armatures of relay this talking circuit is connected to conductors 16 and 11, leading to the iront cord 42. Through the armatures and contacts of relays 9| and 92 thistalking circuit is connnected to conductors 18 and 19 leading to the tip and ring of the rear cord 3l.

Dialing In order to dial on a cord circuit the talk and dial key 62 of the cord circuit is operated. When the dial is moved oi normal relay 93 operates in a circuit which may be traced from ground, springs 2 and 3 of key 94, the off-normal springs of the dial 95, winding of relay 93 to battery. Through its front contact and armature 2 relay 93 short circuits resistance 96. The operation of relay 93 also results in the operation of relays 91, 91 and 99. The circuit for relay 91 may be traced from battery, winding of relay 91, front contact and armature 3 of relay 93 to ground. The circuit for relay 81 may be traced from battery, winding of relay 81, iront Contact and armature 4 of relay 93 to ground. The ground for the operation of relay 91 may also be traced through the armature 5 and back contact `of relay 84, the lower winding of relay 90 to battery. Upon the operation of relay 91 ground is extended from armature 2 of relay 91 and its front Contact through the upper Winding of relay 99 to battery. With relay 91 operated the attendants receiver is short circuited at the armature I and front contact of relay 91 for a sumcient length of time to prevent an undesirable click when the dial restores after dialing the rst digit. This also prevents the attendant from hearing transmission of the dial pulses. With relay 90 operated the attendants telephone circuit is disconnected frornconductors 16 to 19. Through its armature 2 and front Contact relay 99 causes the operation of relay 92. At this time a short circuit across conductors 16 and 11 may be traced from conductor 16, conductor 98, the contacts Yof the dial 95, armature 2 and front contact of relay 93, front contact andv armature 4 of relay 99 to conductor 11. The retardation coil 99 is short circuited through the front contact and armature 4 of relay 92. The operation of relay 92 splits the cord circuit leaving the impulse springs of the dials connected to the front cord over leads 16 and 11 and battery and ground through the windings of relay |00 connected to the rear cord over the leadsr 18 and 19. Relay |00 operates over the station loop or through the retardation coil bridge in the cord in case the receiver at the station has been replaced on the switchhook. Dial impulses are transmitted over the circuit to which plug 42 is connected in the usual manner. When the dial has completely restored relay 93 releases. With relay 93 released the short circuit is removed from the parallel combination of the resistance 96 and retardation coil 99 and relay 91 is released. The release of relay 91 removes the short circuit on the attendants receiver ,and releases :the relay 90. Relay Sil. released removesthe shuntof the resistance 4S155 about Vthe retardation coilllSand closes the attendantstalking circuit. The .retardation coil 89 now holds the connection, the circuit being .traced from conductor lfthrough'the impulse springs of the .dial 95, .the retardation coilll, front contact and armature .4 of relay 92 .to conductor Tl. The front and rear cords of the associated cord circuit `are connected through condensers |01 and |02 to enable the station to talk on theconnection incase the attendant fails tti-restore the .talk and dial key of the. cord after dialing. When thetalkand dial :key 62 is vrestored relays land 92 release. With relay l92 released relay 8l .is released. Relay 8l being slow in releasing will :keep the receiver open long enough to prevent clicks to the attendant dueto the release ofxthetalkand dial key in .the cord circuit.

Front cord inserted in attendants connector jack The circuit `functions as described above. Relay li'i is connected to leads. 18 and 19 `after relay 9,2 operates and is held operatedA over the station rloon if` the rear cordis connected to a station. If the rear cord is connected to. acentral oice trunk', `battery and ground throughfthe windingsof relay Idil.. will be Connected respecti-vely'to` ground and battery iromthe, central cnice duef to` a reversal in the cord circuit and relay lll will therefore, be operated. When the dial returns .to normalrelaysBB., 97| and .Sl lre lease but relay .i90 remains operated holding relay, 92, whichinturn holds relay 81.-. operated.

When the attendant has finished dialing the station number the attendantsconnector cutsV through in a` manner Which will be hereinafter described. This` action results in a reduction of the sleeve, resistance so that. marginal relay :iid now becomes. operated, in turn operating relay 4,5, Duringthe operation of the. talk. and dial key 62, a `circuit is` established irjom ground, springs l and. 5 of` key springs Hand I2 or" key 52 to. thawinding of. 'relay' 5ft. and thence to battery whereupon relay Silbecomes operated'. Now upon the operationof.. relay .llj acircuit is established from. ground," iront Contact and armature $54 of relay llf, front contact and armature d oi relay 510 to the winding of relay IlllY which nowv becomes operated; Relay V`|ii3 operated opens the circuit torelay |00 which releases and allows relays 921 and 8T to release. In this way all the relays `in .the dialing circuit restore to normal andleads 76. and 'IlV of the cord are connested Yto leads 1 8' andV 19.

Monitoring 'Ihisytelelihone circuit-V is arrangedwith a. po.- sltiorl: monitoringkey.'A Iithe;-.key 9i :is operated and then the talk and dial key 62..oi-a cordcircuit. is operated the attendant can monitor on the particular cord whosefkey. is operated. 'The operation of theposition monitoring key :lerenioves ground. from springr 4. thus allowing rerlay.. iiii to become releasedand at the saine time causesrelay 8.4; to become energized. Relay 35| operated connectsvthe'- attendants telephone rec eiver. acrossthe cord, througlrtherepeating coil |34, the restof.- the,telephoneoircuit beingf disconnected from the receiver at this time. The release. ofgthe. position; m.en .itorinaA kewreeases relay 584:, i

Jacks 82 and 83 are for theuse of the operator and jacks |05 and |36 are for theuse .ofthe supervisor.

A plug seating circuit is `provided to insure against preliminary impulses .during plugfin. This'comprises a pair of relays |63 and |09, the rst of which is a two-step relay. When relay |68 is energized-through its lower winding itwill move its armatures v3 and 4 b-ut-willnot move its armatures I and 2, This is indicated by the fact that armatures and '2 vare shown heavy and armatures 'J and 4 are shown light.v vWhen `a plug, such as plug 42', is inserted `in jack4 ill? and the .plug becomes fully seated, then a` connection is made `betweenthe ring of the lplug and the ring oi. Vthe jack |67 which may be traced through varmature 2 and backcontact of relay |08, back Contact and armature l of .relay thelower winding of relay |68 to ground. Since battery is supplied by the ring of the plugoi the cord circuit, relay |98 movesits arrivai-.1.1res..3.y and 4. Thereupona connection is made from rpositive battery, winding of` relay All, winding of V.relay i3 and the sleeve of the cord in cord circuit, Fig. `3, through thesleeve of jack il, arma.ture and front contact of relay |7138,Y winding of relay |59 to battery. Relay |09 operates and establishes aconnection from battery, upper winding of relay l, armature 3 and front contact of relay lljarmature 3 and frontcontact of relay lila, the lower winding of relay |03 to ground. Thus the two windings of relay |58 are placed. in series and this relay thereupon fully operates and attracts all of its armatures. Y In itsnorr'nal condition a circuit is established from battery, through armature 2 andback contact of relay |95, through the'back ContactV and armature 3 of relay H8 to the idle indicating lamp IIS. Therefore, upon the operation of relay !69 thisidle indicating lamp is extinguished and the battery connection isv extended by armature 2 of relay |09' to its front contact to cause the lighting of the nextidle indicating` lamp.

Upon the operation oi relay |68' the tip con# ductor is extended'over armature l and'V iront Contact of relay |08, the upper left-hand winding of repeating coil `2'l, back contact andarmature fl of relay |`|l'!',the upper winding of rel'ay'l |2 tov ground. YIn asimilar manner the ring of jack` |01 isextended from 'amature 2 and front Contact or relay |58", lthey lower-'left-'hand winding of repeating coil |21, backcontact and armature G of Vrelay Ho', the lower winding of relay H2 to' battery. Due toareversal inthe cord circuit hereinbefore explained, relay I t2' tiecomes operated. The operationof li-ne relay M2 connects the windings of the polarizedrelay |554 tov the distantconnectory circuit-which has a relay facingthe lineto this `trunk circuiti. This connection may be traced asv follows: Afrom ground, through thelower winding of relay lf M; armature2 and front contactiof relay H2?, the lower right-hand winding of repeating coil` i111, conductor H5; back Contact` and arma-ture :1f ol relay `|2'3 toconductor. |25..and..a. similar circuit from battery,y the upper: winding. o 4relayA i.' |41, armature and freni-.contact of y 1.5.2,. the upper right-hand winding ot repeating: coili 1;, conductor H6; back contact; and armaturerticiv relay |23 to.` conductor |24,A Relay Hit-'operates in this circuitnandfcauses the` OperatiOnofre.-

lays IIl' and IIS. A circuit may be traced from battery, winding of relay lI'I, bacl; Contact and armature 3 of relay H0, armature and left-hand contact of relay Ill, armature and back contact of relay H9, armature I and baci; contact of relay II to ground. Relay III, in operating, connects ground through its armature 2 and front Contact to the winding of relay IEB.

When the attendant dials, relay II2 follows the dial pulses and opens the line to the distant connector each time it releases. The polarized relay ||4 follows the dial pulses as repeated by relay ||2 but the slow-release relay III holds operated. l

When dialing is completed the distant connector circuit insertsl a high resistance into the line causing relay IUI to release. The release of relay I I causes the release of relay I I'I which, due to the slow releasing characteristic of relay |I8, results in the operation of the cut-through relay H0. A circuit for this relay may be traced from ground, armature I and front contact of relay |09, armature 2 and front contact of relay I I8, back contact and armature I of relay IIl,the Winding of relay |I0 to battery. Relay IIO locks through its armature 5 and front contact and the front contact and armature I of relay |09 to ground.

The operation of relay H0 causes the resistance in the sleeve lead to change from high to low. Up to this time the winding o relay |09 which has a high resistance is connected to the sleeve of jack il but upon the operation of relay ||0 a lower resistance |29 is placed in parallel with the winding of relay |09 so that the marginal relay d in the cord circuit now becomes operated. The operation of relay ||0 also connects a condenser across the middle of the side of the repeating coil facing the distant connector and prepares a circuit for connecting the windings of relay IIIl with polarity reversed to the leads of the distant connector through normally closed contacts of relay ||2 and the windings of the diierential relay IIS. The operation of relay I I0 opens the circuit of relay |I'Z so that this now releases. Relay ||0 also prepares a circuit for giving a closure to the cord circuit through the contact of the polarized relay I I4.

The change in the sleeve resistance to the cord circuit resulting in the operation of the marginal relay 4i causes the cord circuit to send out ringing to this trunk. The ringing current causes relay |22 to operate which results in the operation of relay |23, thus causing a clear path from the tip and ring of the jack lill to the line conductors I2 and |25, respectively.

When the called party answers or when the distant connector connects a low resistance ground to the ring lead as a line-busy indication during the ringing interval, the tripping relay inthe cord circuit operates and removes the ringing current, causing relays |22 and |23 to release. The release of relay |23 again places the polarized relay IIl in circuit to operate over the station loop if the line is idle, If, on the other hand, the line is busy and the operation just described has been caused by a low resistance ground to the ring lead, thenV the differential relay ||9 will be unbalanced as a busy indication and instead of connecting a bridge across the tip and ring of jack Il, will now connect interrupted ground to the ring of jack |01, leaving the tip thereof open. In case only relay ||4 operates as a signal that the called party has answered, a circuitmay be traced from the' tip of jack |01, armature I and front contact of relay |08, the upper left-hand winding of repeating coil I2I, front contact and armature 'I of relay ||0, back contact and armature of relay I I9, left-hand contact and armature of relay IH, armature 3 and front contact of relay III), the lower left-hand winding of repeating coil |2I, front contact 'and armature 2 of relay |08 to the ring of jack |01. In case the signal coming from the distant connector is a low. resistanceY ground on the ring, thereby causing the relay ||9 also to operate, a connection may be traced from the ring of jack |01, through armature 2 and front contact of relay |08, the lower left-hand winding of repeating coil |2I, front contact and armature 3 of. relay ||0, armature and left-hand contact of relay IIlI, armature and front contact of relay I I9 through retardation coil |21 and interrupter |28 to ground. Upon the first open period of this circuit, the flashing recall circuit in the cord will be prepared for operation and then put into operation upon the next closure through the interrupter |28. Thereafter the signal displayed in the cord circuit will be modified by the interrupter |28.A Since this is of one-half the rate of the interruptor causing the flashing recall signal,the result will be a totally different kind of visual signal in which thevdisplay is of `approxin'iately three-tenths of the period and the dark condition oi? the lamp is approximately seven-tenths of the period. In other words, every other ash of the lamp in the 'flashing recall circuit will be eliminated. A's mentioned hereinbefore, the'interrupter |28 is synchronized with the interruptor 66 of the cord circuit so that the relation between the two is iixed.

When the called line is idle and the ringing has been tripped, conversation may take place with the transmission battery for the called party furnished through the windings of relays I4, I9 and the repeating coil |2I. The contacts of relay ||4 maintain a closure toward the cord circuit land relay II4 will receive switchhook flashing from the called party to the cord circuit so that a flashing recall condition' may be set up in the ordinary manner by the subscriber reached through the distant connector.

When the plug is removed from the jack, relay |09 releases causing the release of relays |08 and Illl. The release of relay H0 causes the release of relay I and relay IM, except that this latter relay may have already released due to the called party hanging up. The release of relay ||1 causes the release of relay ||8 which causes the idle indicating lamps to light and restores the circuit from the lower winding of relay |08 to the ring cf the jack |01 so that it can operate on the next call.

Connector circuit for completing calls from attendant at distant private branch exchange to station lines-Fig. 6

Upon the seizure of the circuit shown in Fig. 5 and the operation of the line relay ||2 thereat, battery and ground are connected through the windings of relay Ilfi to the conductors |24 and |25 which extend to the upper and lower windings, respectively, of line relay |29. Relay |29 operates from battery on the tip and ground on the ring of the trunk circuit and causes the operation of the rst slow relay |30 in preparation for pulsing.

On the rst open period relay |29 releases and establishes a circuit from its armature I and back Contact, through armature #I and 5frontfcenta'ctof rel-ay |730, springs f6 and S the vertical el'normal spring combination 4131i, 'th-rough fthe -Windings of lslow-'release relay 432 and *the `Vertical magnet lil-3 `to battery. Relay P312 `'operates -before the Vertical magnet lsteps the switch, opens the vcircuit of Jrelay |34 4Vclosesits foivntlooking circuit to spring -5 of the --Vertieal off-normal springs 13|. Wh'enthe'swiths'teps and theyertical off-normal springs operate, the original noperating circuit -for vrelay 4| 32 andrnagnet W73 will be opened but-a substitute circuit throughithe'a-rmature of relay l|32 Awill be 'closed A'in `its place Without interrupting'thesstepping circuit. When the 'line relay |29 'reoperates Athe `vertical `magnet releases, but relay 432 Lbeingslow -to xrelease `holds until theend of the train of 'impulses comprising the rst digit.

The switch thus continues tostela yertiearuntil theend of the trainfof impulses Whenfthecperation'of relay lt'rele'ases relay 132.

YOn Athe second digit, when relay 52e releases, relay |54 and the rotary magnet 1'35 operate. The 'circuit may be traced Afrom armature *l and backcontact of relay |29, armature i| and front Contact of relay 4%, Avsprings *6 and 5 o'f the 'vertical oir-normal spring combination ttl, Varmature and back lcolitact of krelay :I3-2, 'armature and back contact relay'l, through thewniding ofrelay l| 'to battery andinpaiallel ytherewith through armature it 'and back `conta-ctfof .relay itl' and 'the Winding of rotary magnet IA|355 te battery. The rotary magnet vvand relay HE are in multiple and the AAlatter Irelay"being s'loWto release remains operated during -pulsing -While the rotary magnet y*steps theswitch tothedesired terminal. Y Testing the line-Line busjy When theswitch Ais .onthe line lto `Which `ithas been dialedand betere thesloW-release relayld releases, .the .sleeve yoi the ycalledline iis .connected to rela-y |38. Arcircuit =may be traced from battery through ythe `Winding .of Yrelay 4.38 V.tronto/ontactand armaturel of.relay.| ,.sloeve brush .|39 to the vsleeve terminal of the .oalledline .On a busyline the sleeve will be .groundeiitherebyoperating relay |38. Whenrelay |34 releases, relay |38 locks through 'the normal contacts .of Vvarrnatore? of relay 131|, front Contact and armature .2 of relay |38, armature 3 and 'front contact of the first 4slow:releasing relay 'i Sil to ground.

Relay operated, the circuit-,of .relay i?? and operates 'relay T315. This lcircuit may be 'ced from battery, Winding of lrelay i! 36, l annatuie 3 and back contact of Lrelay |34, -rrontcentact and armature 3 or" relay 113B to ground. 1Relay |26 operated, (l) :opens'the `'cineuit of vrelay .lu-lil the circuito'f lrotary magnet 4535, (2) re'-l r ves `the line relay |29 from the tip and ring, thereby Vca Vthe release of VIrel-ay |329, 'and 1(3) connects high resistallre'e 'relay fll through the armature :and .back .nontactfof relay f|1|1l and .the .iront Contact :and :armature if relay das to the tip Wire :VM :and :high :resistance relay 12, through armature 5 and Ehacl: foontaotroi relay the front I'Contact :and varnfratlme *l fof Irelay tothe ring-conductor .Relay |42 operates to 'ground on .the ring :fat `.the distant fend of ithe trunk and holds the firstfslow relay til operated.

Removing the line relay .|29 :from the tip `and ring isasignal to .the ftrunkat the distant private ranch exchange to .prepare to ring .creto receive busy flashes and when the trunkis .thus prepared it reverses ybatteryar-ld ground to Lthe -connector circuit. Relay M2 then releases and relay NG thenoperates. Relay flil closes resistance |45 across the "windings of relay 'IES which there- Lupon operates and holds -the rst slow relay |33 operated. Relay `Hill also completes the circuit to re'l'ay lll through'the armature l2 and front lcontacter :relay |23, armature '3 and lront Contact of relay |56, to ground. operating, relay vM3 establishes faconne'ction from ground, armature 2 andnront 'Contact fof .relay lat-3, front Contact and armature '.-o'f relay |233 to 'the :ring conductor |25 'extending toiv A'outgoing ltrunlrcircuit, Fig. 5, .Where :it results .in Vurrbalano'ing the `differential relay |53 for the purposeshereinhefore described.

/Whenthe :calledrline `is 4idle, thefsleevebrush .l 39 will encounter e. ibattery :connection `instead of grounrlnnclzrelay |35. :in :releasingat'the end of the rotary sstenping 'movement connects'relay 1| 3l totheslee'vte bluish. :This circuit may be'traced 'rom sleeve Thrush 139 through farinature 2 .and back on'tact `:offrelay .434, Supper Winding of vrelay |;3i| hack Contact :and mature .2 .oirelay |3t, .armature :3 .fand V"front fcontact :of the rst slow .relay lzl. .iR'ela-y itl becomes suiliciently enerin thiscircnitto move Vfits f-armature''wl'iieh foloses a circuit from ground-.armature 2 -andJfront Contact of rel-aylrejront vcont-att and armature '2 .of :relayfi 31, lower winding v'of 'relay |31, through rotarymagnet |3251to battery. This causes 'the full Aenel-gi'zati'on o1" relay 'l 3.1 and Aat the 'same .time lstops *further action the rctarylma'gnet. 'Relay Etf? connects ldirect ground Aforward to the line roircuit'sleeve'tlncough 'its front Contact and armature ".6 to hold the 'cub-orf relayrof the called :line :and 'to birsy "the terminal te other switches. Relay d 3 l :also opens fthe original energizing 'circuit rior :the 'rotaryma'gnet and :opens the release path through its armature l. Throughiit'sarma- .tures and 3 relay |37 .partiallyfcloses the Vtin .and ring conductors tothe called station. I l

Upon the release of relay .maand the operation of relay '|31 a circuit is established from ground through the front Contact and armature 5 of relay El?, back contacta-nd armature Aofjrelay Vfl-lll l"to Ethe -win'dingof relay 1135i. hereirbe'fore f' iiescrib'ed, relay fltnpon operating, removesthe lineirelay 2| 2B from the 'tip and ring 1jand kcloses the twdhig'h 'resistance relays F' and |122, respectively, te the tip and ring -of the trun'k. "Relay -fE-Ellolds lrst A'slow relay il-operated until battery is reversed by the trunlfireit at the private branohfexehange. Relay `lllvthen Afreleases 'and relay fli4l!) operates. i-Relay l'il aga'inrc'auses the operation ol the Aline -relay FZ5 to Ycomplete the circuitto relay H3 which now operates. 'Relay l| 1X3 operated, connects the tip and ring of the trunk `from the distant private branch exchange tothetip and ring-ol the-called station. 'Thetip conductor #Eig Y"may "be traced `through the upper Winding ol the 'supervisory relayV |1313, through armature i and front VAcontact of `relay l'gfront contact and arma-ture I or relay *iiito the tip brush '|155 of :the connector which is lnovi in assoc'iat'i'onwith the tip oi the called line "Hl-7. The ring 'cenductor |25 he traced through the lower winding of relay LHill,armature 4 andfront Contact of relay 'l d'3, 'frontfcontact `and larmature il ofrrel'ay it? tothe ringhrush 'tilt ol" the connector leading to the called sbsoribers station 1M. Relay 53, irl-operating, opens thecircuit -o'f'relay |512 but relay i is still connected to the tip so that the line relay |29 `remains operated.

During the ring'ngofrthe station :from-the distant private branch exchange, relay |69 holds to the ringing `ground o-n the tip. VRelayV ist, `Whose lower Winding is in series Withthe `ring,'may operate on the alternating current and operate relay This will open the winding of relay |45 but its lower contacts perform the same function as the lower contacts of relay it@ so that the line relay remains operated to hold the connection.

When the called station answers, ringing is tripped and relay |45 operates on the station loop to remove relay it@ from the connection and hold the connection through the operation of relay IM as described. Upon disconnection by the called station relay iff-fl releases and causes relay |4| to release, but relay lili! then operates to ground on the tip to hold the switch.

When the cord is pulled down at the private branch exchange after the called station disconnects, relay E55 will release thus releasing the line relay |29 and the iirst slow relay |39. Relay |55, in releasing, opens the circuit for relay |31 and now a circuit may be traced from ground. armature l and back contact of relay |29, armaature l and back contact of relay |35, back contact and armature 'I' of relay |31, springs and 2 of theV vertical off-normal spring combination iti, to release magnet |45 and battery. Release magnet |59 is operated and causes the brushes U55, |538 and |39 to leave their position in connection with the terminals of the called line. Thus, the switch is returned to normal. The release of relay |37 causes the release oi' relay |55 and the release of relay |29 causes the release of relay |43.

On disconnection by the attendant from a busy connection, relay in releasing, releases the line relay |25 and the first slow relay |35. Relay ISE) then releases relay |38 which, in turn, releases both relays |55 and |53. the release magnet operates to restore the switch to normal.

Connector circuit-Rotary hunting-For complating from attendant at distant private branch exchange to station Zines-Fig. 7

The operation of this connector is in many respects similar to the operation of the connector in Fig. 6. When the attendant at the distant private branch exchange selects this trunk, the line relay |55 operates from battery on the tip and ground on the ring of the trunk circuit at the distant private exchange. Relay |55, operated, operates the first slow relay |51 which prepares the circuitl for pulsing.

On the first open period relay |55 releases operating the second slow relay |52 in series with the vertical magnet |53, through the springs of With relay released,

the vertical Cif-normal Contact combination |54.

Relay |5| being slow to release will remain operated during pulsing. Relay I 52 operates before the vertical magnet steps the switch. opens the circuit of relay |55 and closes its own locking circuit to the vertical off-normal springs. When the switch steps and the vertical ofinormal springs operate, the original operating circuit of relay |52 will be opened but the holdiner path will be completed without interrupting the stepping circuit. When the line relay reoperates, the vertical magnet releases but relay I52 being slow to release holds until the end of the digit. The switch thus continues to step vertically until the end of the digit when the operation of relay I 55 releases relay |52. On the second digit when the line relay |55 releases, relay |55 and the rotary magnet operate. Relay |55 being slow to release holds over pulsintr while the rotary magnet Steps the switch to the desired line terminal which may be either an individual line or the rst of a group of lines.

geez/isi Before relay |55 releases at the end ol rotary stepping a path is closed from the sleeve wiper |55 of the connector switch through armature 2 and front contact of relay |55, armature I I and back contact of relay |51 to the winding of relay |55 and thence to battery. A busy line will have ground on the sleeve which will operate relay |58. When relay |55 releases, relay |58 locks to the sleeve ground through its armature l and front Contact and the normal contacts of armature 2 of relay |55 to the sleeve wiper |58. Relay |58 at this time causes the operation oi relay |60 in a circuit from battery, winding oi relay |58, back contact and armature I of relay |55, front contact and armature 2 of relay |58 to conductor I5! supplied with ground over armature 2 and front contact of the rst slow relay |5|. Relay |55 operated, (l) opens the circuit of relay |55 and the circuit of the rotary magnet |62; (2) removes the line relay |55 from the tip and ring which now releases; 3) connects high resistance relay |53 to the ring conductor |25 and high resistance relay |54 to the tip conductor |24; and (4) closes a circuit from relay |55 which may be traced from battery, the winding of relay |55, armature and back contact of the rotary magnet |52, normal contacts of armature Z of relay IE5, front contact and armature 5 of relay |53, armature G and front Contact of relay ISG, armature I and back contact of relay |59, front contact and armature of relay |53, to wiper |66 of the connector. Relay |53 holds to ground on the ring at the distant Yend of the trunk and holds relay I5| operated. v

If the busy line is the rst terminal in a group of lines, the bank terminals cooperating with brushes |55` and |66 will be strapped together as indicated in the second group of bank terminals where direct connection is shown between bank terminals |51 and |68. Y'J'."nus, the busy potential of terminal |61 will be connected to terminal |53 and thus communicated over the lcircuit just traced to operate relay |55. Relay |65, operated, causes the rotary magnet to operate in a circuit which may be traced from ground on conductor IBI through armature and iront contact of relay |55, armature IU and back contact of relay |51, winding of rotary magnet |52 to battery. Since relay |55 and rotary magnet |62 now mutually control each other, the switch will step automatically until an idle terminal is found or the last line yof the group is encountered. Relay |53 being slow to release holds during this stepping and will remain operated so long as busy lines are encountered. v

The switch will not step beyond the last terminal in the group since the terminals |69 and |75, cooperating with wipers |55 and |55, respectively, are not strapped ltogether and there will be no operating circuit for relay |55 as de scribed above. Relay |58 remains operated from ground on terminal |59 and an operating path for relays |59 is found from battery, through the winding of relay |55 to ground on the sleeve. During rotary stepping on terminals other than the last, relay |59 does not operate since it is bridged across the leads which are strapped together on these bank terminals. Relay |551.7 operated, locks 4itself and relay |53 to ground on conductor |5I and opens the circuits leading to wipers |55 and |56. Relay |55 does not operate i-n series with relay |59.

The Operation of an individual busy line is V line is idle, relays teg-and ring as describedabove 1is1a-signal itotheltrufik that the V.dista-nt.: private .branchs exchange to fprepare to ring or to receive a busy indication and when the trunk is .thusprepared -it-reverses bat- -tery and vgratin-cl'to'fthe nonnectorlcircuit. *Relay.- i553 then releases. and Irelay-' I64.=operates. Relay '1154 closes resistance P7-I -lacresslthe-Winfdlrrgs of the line relay `i553 Wliih'opera'tes-.andihlds Atlf-ie "rst slow. `relay Vl'5'l. Relay -|53 completes the circuit `forreiay .H2 lwhich closes v-grouz1ld eto vthe ring -of the trunk "to @the ldistant private branchexchange asa busy indication. Tli-islast connection may Eloe 'traced `frem ground, front contact and armature 516i relay lllz, Varmature -5 andback contact of relayl5'lfto the-ring conductorA l 2'5. Thisfas described 'fl-:iereiribforef'op- :erates'the di'ferentalrelfay H59 1in the-'outgeing trunk circuit 'and causes the..eocalle`d1synco pate'd signaltobedisplayed inthe cord circuit.

If the irst line of tliegrcupfo" 1an iii' d' When relay 55 releases, Inehupperfviindinf,r` relay EE'l is closed-tothe sleeve wiperf tery tlircueh .the cut-olf relayfen thesleeveloank operates `armature AE of l.relayi Tl aifhielrleses circuit 'for `the vloyverii riding thereof to `ceinpletely operate relay f grounds the lsleeve Wiper 55 'tobusy the -l` `andto held the cut-eil vrelay ope`rateel vpa;` l. y closes the tip `and ring vof -the'line texrtheltrunlr., opens the rotary magnet, release andthe circuitof relay V58 vandpreparesftlie Acircuit ci relay VIZ which will becomeeffective upon, "t'lie reoneration of the'line relay? tt?.

when vrelay l'lil operates Von Ybattery reversal from the Strunk circuit Aat tlre distant private branch exchange, relay itillroperatestn `complete i the circuit for relay V2. Relay l-l2, 1operating, remores relay E53 fram "the ring cf the trunk, closes the `tip and'ring o'f .the trunk -to tlf-ie ltip and ring of the statien, and locksinependently el the contacts fof relayi. -Duringringing'from the distant private fbranch exchange i551! holds to'ringing ground on the tip. The suner- Y visory relay 173, Whose windings are iin Vseries with the line to the 'called station, -mayeperate en ringing current and operate frelay Relay Elfi opens the circuit of relay lifl but since its armature Fl and front Contact crm thesa'me operation as the armature and. front Contact ci relay H150 land, .the :first slowuzelay ali. Relay :iii releases l:relay :l 5:7 which ioperates the Vrelease :magnet H575 itnirestorethe sivitchfto normal and freleasesmelays dei) nand 51. @n :disconnection byzthie attendrai-it:from .fa busy connection, relay rfli' releases :relay fk5-i .Whichnperate's tlie release magnet to restore the switch to normal. Relays sl55', fi E3, :iz and l-IZIZralso release.

A Yplugseating circuit is provided to insure r -at preliminary impulses during :plurale .TW-herir .plugissfully seated battery on the 1 oiithelcorrl operates relay il?? to oper-'eteitsY irnatu-rfel only. lhi-s.closes-tlie sleeve c-etl'ie lacie to Aiin-leer winding er relay lill Relay @perales 'fend extinguishers the -iclle indicating lamp Jie. Normally v.thecimrt `may he traced igreundlthrougti lamp springs -5 and IS- of the vertical isili-normals combination Ytrackmenta/ct and armat "e l2 -orrrelay il linearer-lie operation vof tn-A circuit is opened .and battery is extended tliieugli ture -2 aand `its iront .Contact -to -tlie corresncndine: armature of the next correspending relay lill for operating -tlie idle .indicating ilamp of the nextridlecircuit. The oper-ation .-y-lfi closes `a circuit through levier .finding er relay rI-'' `to:fullyseperate this `relu-y. Relay/il?, fullyfoperated, epensfits-cwn upper Winding closes `the `.tip 'and f 'n-g of jaclf: il@ to `ground and battery, respectively, through the windings efthe line relaylti. .Relay lill sisef 483 for purposes :te-beadescrileedllmcnaitw The Eline irelay 432: 'operates .from bridge rin the cord circuit fand :ener-giace are ay i-.fwhich loclrstog-rnimdthrougli its armature contact, fermeture 11i beek `centac't .185 .to ground `ver1 cenductor l nowlreadyffoiapulsing. Gn the first en the dial, relay I8? releases cperatir Y `in .series with the vertical .inagnet Relay relay relay wie 'Will be maintained operated to hold tliefconnection.

"When 4the "called line answers ringing is trinpefl, 4relay lli; operates :on vthe Ls'taticn loop to remove relay iii@ from the connection anelito hold the veennection througlritlie operation 'df relay illias described. fOn disconnection by the called statici-relays il?, and i-if/l release but relay i 11 holds the switch.

When the switch. in rotary Vhunting :cir-er busy lines as described above steps `te an 'idle line, relay ii releases becausefc-fabsence of busy `pstential on Vthe sleeve but `relay 'which 'lia'cl operated from relay reine-ins operaterlthrough locking contacts to insure t .t tne 'battery 'and ground frein the'line relay are.notagain-con`- nected to the and ring; 'Relay lill foperaltvon the idle lne as described above 'cannet operate until relay i233 releases and it is, therefore, necessary to lock :relay :i511 operated.

`when the cord is AApulleddownvaftertlre:station disconnects, Vrelay l-flxreleases releasing fthe Aline 4.86 eperates lbetere the vertical ma eps the switcnfopens .the circuitirelay l e3 and closes its zown y locking circuit Vto it-he -ierticaloirnormel springs. IWhen thefswitcli estepszancl the vertic offanermal ysprings i150 spera-te, tlieenerating Ormel/ay tli will belepeneelbut the vpetit will fbe comeleted -withaut interrupting the stepping rircuit. Twhen ztlee line Arelay i 82 recperates the vertical magnet releases but relay 88 fbeln"V slow to release liedsr-,until tlie rend fe'i `the di li'heswitch .ftlius 'continues te sten ically until the endfof :the digit-,when the ation er" relay E32 releases relaylSG. l

lreley 4l On the .second fdigit the line Slt the retarymagnet operate. 'Thecireuit'ier this op etat-ien lmay -be traced frein gre-und, asn/iature 3 and.V back Jcontact of relay i133, :armature and back Contact of relay 182, armar. re iront ccntact'of relay VHllLsprings transl l -ol the vertical effhnvrinal spring comolnn 'i fill. "weer tureand Aleacla,fcontacteef relay 3 and baci: 'centaetof Arelay 'i756 thm-ugh J he Wind ing of relay 16B `and yin pareille ether back-contact :and Parma-ture 3 magnet |52 to battery. The rc ary l and relay 1.88 :are iin multiple out lrelay it heine sloiv fto :release remains .eperated during pulsing,T while the .rotary magnet :steps tneswitch 'to `the desireuline'terminal.

Whennthe .switch iis cntlie line Aft'o which it hsl'ieenv Idaled and fbeftire'the 'Slew release relav 

